Numerous attempts have been made to modify polymers in order to make their surfaces more acceptable to dyeing or painting. Most of the known modifications have been made on the polymer after it has been fabricated, i.e. made into sheets, fibers or other articles of manufacture. One of the methods employed to modify the surface has been a nitration of that surface. Thus, for example, U.S. Pat. No. 3,305,297 teaches the nitration of fabrics with nitrogen dioxide to increase the uptake of basic dyes. Another patent, U.S. Pat. No. 3,583,962, teaches a method of cross-linking by reacting a nitrated polyethylene with diacyl halides or alkali hydroxides. The nitration had been accomplished by reacting polyethylene with nitrogen dioxide. Nitration has also been accomplished by employing radio frequency electromagnetic radiation as an activator of nitrogen dioxide in U.S. Pat. No. 3,761,299. This same teaching also is found in U.S. Pat. No. 4,072,769.
In yet another reference, U.S. Pat. No. 3,879,358, nitrogen tetroxide is reacted with an unsaturated polymer to produce a saturated chain containing nitro groups to which acrylic monomers are then grafted.
According to presently known technology polymers are made more adherent to paint by nitrating the surface of articles fabricated from such polymers. Thus, any apparatus designed to nitrate such surfaces must accommodate a variety of shapes and sizes, or a different apparatus must be designed for each kind of article. It would be desirable if the nitration of the polymer could be accomplished prior to fabrication so that an article fabricated from such nitrated polymer would then readily accept paint.
The present inventor has discovered that when a polymer which has been nitrated is fabricated in a particular manner, i.e. cooled in contact with a polar surface, articles of manufacture which accept paints or dyes more readily are produced.